We've just received the street version which has the softest durometer. See below. It will go on our Exige immediately. I'll report back soon.
I met up with Tim last week and test drove his Exige 'S' with a very stiff (high durometer) PUR engine mount kit. The shifting action and throttle response was excellent. The vibration was.....too much for street use. Track focused cars will be happy with this kit as it great improves the response of the car.